[OT]: bash or any other $favourite{shell}? [was: Wish list]

[Peter Corlett]

Chris Benson <chrisb at jesmond.demon.co.uk> wrote:
[...]
> Ah, that may reduce my interest in UML before the book even arrives :-) I
> was hooked by the promise of UML sharing the host's o/s image, but that
> uses Copy-on-Write ... so I'm unclear whether local changes in the child
> will be visible to the host.

Well, it is possible that UML does have the capability, but it seems
unlikely. I have no experience of it to say one way or the other.

Basically, virtualisation falls into two camps:

a) chroot-on-speed, e.g. linux-vserver, FreeBSD jails, Solaris zones.
   Everything runs under the same kernel instance. It's a very lightweight
   scheme. Linux-vserver suffers from some interesting gotchas due to the
   single kernel instance, and I imagine the others are similar.

   Due to the single kernel instance, there's only one thing accessing the
   filesystem so the controlling/root server can access the filesystems.

b) Individual kernel instances that run separately, e.g. UML, Xen, VMWare.
   Everything looks and acts like a physical machine. It's relatively
   heavyweight but the extra separation can make this worthwhile.

   Because each kernel has its own buffer cache et al, it's impractical to
   mount filesystems in use by another virtual server except over something
   like NFS.

-- 
A successful sysadmin must accept no limits on his laziness.
					- Peter da Silva in The Other Place